So a mated pair of angels, a mated pair of rams (what about two pairs?), 6 cories, and 20 rummynose in a 75 will be okay?

Yes in my view, but only one pair of rams. Two mated pairs would be interesting but you would need good territory division especially if intending to have a spawning, plus I'm not sure the pair of angels with two pairs of rams would not be pushing things in the same space. All of these cichlids are just that, cichlids; not particularly rough species, but still cichlids.

Territory division means having suitably-sized spaces separated by plants, wood or even rocks from which the fish can't see each other. They will work to defend their territories constantly if they see others, and they need some relaxation.

You previously asked about caves and I missed that; rams spawn on the substrate using flat stones. I've not used caves, just had the tank divided as above, and they chose their site.

The aquarist is one who must learn the ways of the biologist, the chemist, and the veterinarian.[unknown source]

Something we all need to remember: The fish you've acquired was quite happy not being owned by you, minding its own business. If you’re going to take it under your wing then you’re responsible for it. Every aspect of its life is under your control, from water quality and temperature to swimming space. [Nathan Hill in PFK]

The aquarist is one who must learn the ways of the biologist, the chemist, and the veterinarian.[unknown source]

Something we all need to remember: The fish you've acquired was quite happy not being owned by you, minding its own business. If you’re going to take it under your wing then you’re responsible for it. Every aspect of its life is under your control, from water quality and temperature to swimming space. [Nathan Hill in PFK]

it all depends on how often you are doing water changes. there is always the 10gal/fish rule but if you pick up on w/cs you can increase the load.I would say a nice school of 10-15 would be ok. I dont know what your w/c schedule is like but I would try and do a 50% every 3-4 days to keep everything in order.I am a big beleiver in big and often w/cs they only thing it will hurt is your elbow from reaching in the tank. but I do see you have 2 angels so your at least on the right track have a good day Evan

Thanks Evan. I generally do a good sized water change once a week but that is adjusted to each individual tank depending how they react. I'll start with 10 and see where to go from there.

I apologize, after looking back into this thread i realized i had already gotten the answer on rummynoses from two very trustworthy members. I apologize for continuing to ask the same question. On the other hand, it did get me one more opinion that is appreciated, so i guess it wasn't all bad.

Thanks everyone. I will be doing two black veil angels, two rams, 6 cories, and start with 10 rummynoses and work around that. Thanks for all the help!